I'd try a solution of BIOLOGICAL washing powder or liquid in warm water. Slightly dampen cloth or sponge and dab gently. ( 1 teaspoon to half-pint water).
I would be more worried about getting rid of the body first, otherwise just use some soapy water and a cloth. If the stain is stubborn then use a sponge pan scourer but be gentle.
a salt solution in water removes blood from textiles may also work on paint...dissolve a good 3 or 4 spoons in hot water and rub down.... I know a man who'll lose the evidence...... leave £500 in a brown envelope under the bush at the end of the road on tue.........
Actually, I'd try just plain cold water first. If you use warm or hot water on a bloodstain , it can 'set' it then it's very hard to remove.
If the cold water doesn't shift it, try the other suggestions.
Chlorine bleach will not necessarily remove blood but WILL remove colour from the paint. As for "setting" the paint - it's on the bathroom wall and well and truly set by now.